Fabrication of Hierarchically Porous Materials and Nanowires through Coffee Ring Effect

We report a versatile method for the fabrication of nanowires and hierarchical porous materials from a wide variety of ceramic materials such as CaCO₃, ZnO, CuO, Co₃O₄, Co-doped ZnO, and Ag₂O. The method consists of evaporation of CO₂-enriched water microdroplets (diameter ∼3 μm) deposited from an aerosol onto heated substrates (<i>T</i> = 120 °C). A variety of porous scaffolds with 1–3 μm sized pores can be generated by tuning the process conditions. Subsequent sintering of the scaffolds is shown to generate nanosized pores in the walls of the porous scaffold creating a dual hierarchy of pore sizes (∼50 nm and 1–3 μm). We propose a mechanism for the formation of scaffolds based on the coffee-ring effect during the evaporation of microdroplets. Ostwald-ripening of CaCO₃ scaffolds prepared without sintering yields scaffold structures consisting of two-dimensional crystals of CaCO₃ that are one unit cell thick. The favorable application of CaCO₃ scaffolds for the enhancement of bone healing around titanium implants with improved biocompatibility is also demonstrated

Viologen-Based Conjugated Covalent Organic Networks via Zincke Reaction

Morphology influences the functionality of covalent organic networks and determines potential applications. Here, we report for the first time the use of Zincke reaction to fabricate, under either solvothermal or microwave conditions, a viologen-linked covalent organic network in the form of hollow particles or nanosheets. The synthesized materials are stable in acidic, neutral, and basic aqueous solutions. Under basic conditions, the neutral network assumes radical cationic character without decomposing or changing structure. Solvent polarity and heating method determine product morphology. Depending upon solvent polarity, the resulting polymeric network forms either uniform self-templated hollow spheres (<b>HS</b>) or hollow tubes (<b>HT</b>). The spheres develop via an inside-out Ostwald ripening mechanism. Interestingly, microwave conditions and certain solvent polarities result in the formation of a robust covalent organic gel framework (<b>COGF</b>) that is organized in nanosheets stacked several layers thick. In the gel phase, the nanosheets are crystalline and form honeycomb lattices. The use of the Zincke reaction has previously been limited to the synthesis of small viologen molecules and conjugated viologen oligomers. Its application here expands the repertoire of tools for the fabrication of covalent organic networks (which are usually prepared by dynamic covalent chemistry) and for the synthesis of viologen-based materials. All three materials<b>HT</b>, <b>HS</b>, and <b>COGF</b>serve as efficient adsorbents of iodine due to the presence of the cationic viologen linker and, in the cases of <b>HT</b> and <b>HS</b>, permanent porosity

Sea foam as a source of fungal inoculum for the isolation of biologically active natural products

<div><p>Due to a rate increase in the resistance of microbial pathogens to currently used antibiotics, there is a need in society for the discovery of novel antimicrobials. Historically, fungi are a proven source for antimicrobial compounds. The main goals of this study were to investigate the fungal diversity associated with sea foam collected around the coast of Prince Edward Island and the utility of this resource for the production of antimicrobial natural products. Obtained isolates were identified using ITS and nLSU rDNA sequences, fermented on four media, extracted and fractions enriched in secondary metabolites were screened for antimicrobial activity. The majority of the isolates obtained were ascomycetes, consisting of four recognized marine taxa along with other ubiquitous genera and many ‘unknown’ isolates that could not be identified to the species level using rDNA gene sequences. Secondary metabolite isolation efforts lead to the purification of the metabolites epolones A and B, pycnidione and coniothyrione from a strain of <i>Neosetophoma samarorum</i>; brefeldin A, leptosin J and the metabolite TMC-264 from an unknown fungus (probably representative of an <i>Edenia</i> sp.); and 1-hydroxy-6-methyl-8-hydroxymethylxanthone, chrysophanol and chrysophanol bianthrone from a <i>Phaeospheria spartinae</i> isolate. The biological activity of each of these metabolites was assessed against a panel of microbial pathogens as well as several cell lines.</p></div